It wasn’t long ago that going without water during a workout was considered a sign of mental and physical toughness. Even marathoners were averse to drinking while racing, believing the time gained by forgoing water stations far outweighed any possible health or performance benefits water might provide.

That thinking started changing in the early 1980s when the first series of studies came out showing dehydration has a negative effect on athletic performance. By the 1990s, the message was so well received that water bottles were plentiful on team benches, and the importance of drinking water before, during and after exercise was drummed into runners, swimmers, cyclists, gym rats and anyone else who worked up a sweat.

But in true fitness fanatic fashion, the idea “if some is good for you more must be better” took hold, and the first cases of overhydration started showing up among recreational distance runners and triathletes. It didn’t help that recommendations by highly regarded organizations like the American College of Sports Medicine advised exercisers to drink early and often. Their catchphrase “drink before you’re thirsty” was a popular mantra among the active set, which took the practice of hydration to new levels.

By the early 2000s, exercise experts were starting to wonder about the validity of the hydration guidelines. Not only was the number of overhydrated athletes on the rise, but it was clear front-of-the-pack runners were successful consuming a lot less water than called for under the recommendations. In fact, studies of the top finishers discovered they had a far greater fluid deficit than those crossing the finish line well after them.

Several studies and more than a half a dozen years later, the ACSM has modified its hydration guidelines, advising athletes it was now OK to let thirst be their guide as to when and how much to drink while working up a sweat.

They prefaced the statement by reiterating that the amount an exerciser needs to drink varies considerably based on several factors, including: exercise intensity and duration, individual sweat rates and environmental factors like how hot it is outside. They urge exercisers to determine individual sweat rates by weighing themselves before and after a tough workout. Any decrease in weight is an indication of the amount of water lost through sweat and as well as a sense of how much they need to drink to keep fluid levels stable.

The goal is to keep weight lost during exercise to less than two per cent, which is when performance starts to diminish. Equally important to monitor is weight gain, which suggests the body is storing too much water that can lead to a potentially life-threatening condition called hyponatrameia. Despite this seemingly simple equation, studies of marathon finishers indicate individual changes in body weight range from a loss of eight per cent to a gain of five per cent.

Clearly, distance runners are still struggling to come up with a practical plan to consume just the right amount of water. No one wants to run 42 kilometres carrying large quantities of fluids. Or do they want to experience the discomfort that comes from gulping down too much water at a hydration station or the health or performance implications of consuming too much or too little water over the course of the race.

So while guidelines are helpful, the practicality of following them can be a struggle. With the summer competitive season in full swing, exercisers are constantly struggling with the question about how best to hydrate. And strangely enough, being directed to drink “ad libitum” isn’t as easy as it sounds. With the number of water stations positioned at regular intervals along most race routes and the rules some sports have about the availability of water during a game, exercisers don’t always have the flexibility to drink when they want. Instead, they must adhere to a predetermined hydration schedule that doesn’t always take into account the weather or their individual needs. So while it’s worthwhile to experiment during training to find out just how much water you need, on race or game day your options may be quite different.

The best solution is to set a personalized hydration plan based on your own sweat rates as determined during training under a variety of weather and playing or racing conditions. Weigh yourself (naked) before and after your workouts while keeping a record of how much water you consumed. Keep weight loss to less than two per cent and avoid consuming so much water that you weigh more at the end of your workout than when you started.

Keep in mind that strict attention to how much you drink is less important for anyone exercising for under an hour. Under normal environmental circumstances, sweat losses during such a short duration won’t be enough to affect performance. That doesn’t mean you should leave your water bottle at home when out for a quick workout under the hot summer sun, just remember you need to drink only enough to match the amount of sweat you expend.

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